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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Er(Al10Cr)2 by Materials Project

Er(CrAl10)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Er is bonded in a 4-coordinate geometry to sixteen Al atoms. There are four shorter (3.13 Å) and twelve longer (3.20 Å) Er–Al bond lengths. Cr is bonded to twelve Al atoms to form CrAl12 cuboctahedra that share corners with six equivalent CrAl12 cuboctahedra, edges with eighteen equivalent AlErAl10Cr cuboctahedra, and faces with six equivalent AlErAl10Cr cuboctahedra. There are six shorter (2.56 Å) and six longer (2.80 Å) Cr–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded in a distorted linear geometry to two equivalent Er and twelve equivalent Al atoms. All Al–Al bond lengths are 3.09 Å. In the second Al site, Al is bonded to one Er, one Cr, and ten Al atoms to form distorted AlErAl10Cr cuboctahedra that share corners with fifteen equivalent AlErAl10Cr cuboctahedra, edges with two equivalent AlErAl10Cr cuboctahedra, edges with three equivalent CrAl12 cuboctahedra, a faceface with one CrAl12 cuboctahedra, and faces with fifteen equivalent AlErAl10Cr cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.70–2.92 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Cr and ten Al atoms. All Al–Al bond lengths are 2.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(BO2)3 by Materials Project

Er(BO2)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are four inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Er–O bond distances ranging from 2.25–2.83 Å. In the second Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Er–O bond distances ranging from 2.26–2.58 Å. In the third Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Er–O bond distances ranging from 2.27–2.52 Å. In the fourth Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Er–O bond distances ranging from 2.31–2.65 Å. There are six inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.53 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.53 Å. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There is three shorter (1.47 Å) and one longer (1.48 Å) B–O bond length. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There is two shorter (1.45 Å) and two longer (1.53 Å) B–O bond length. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.52 Å. In the sixth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.54 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Er3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Er3+ and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Er3+ and two equivalent B3+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to three B3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Er3+ and two B3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Er3+ and two B3+ atoms. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Er3+ and one B3+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Er3+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Er3+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to two Er3+ and two B3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Er3+ and two equivalent B3+ atoms. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Er3+ and two equivalent B3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Er3+ and two equivalent B3+ atoms. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Er3+ and two equivalent B3+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Er3+ and two equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(SiPt)2 by Materials Project

ErPt2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Er is bonded in a 8-coordinate geometry to eight equivalent Pt and eight equivalent Si atoms. All Er–Pt bond lengths are 3.23 Å. All Er–Si bond lengths are 3.18 Å. Pt is bonded to four equivalent Er and four equivalent Si atoms to form a mixture of distorted edge, corner, and face-sharing PtEr4Si4 tetrahedra. All Pt–Si bond lengths are 2.47 Å. Si is bonded in a 9-coordinate geometry to four equivalent Er, four equivalent Pt, and one Si atom. The Si–Si bond length is 2.31 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(BRh)4 by Materials Project

ErRh4B4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Er is bonded in a 12-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are four shorter (2.95 Å) and eight longer (3.18 Å) Er–Rh bond lengths. There are eight shorter (3.03 Å) and four longer (3.16 Å) Er–B bond lengths. Rh is bonded in a 5-coordinate geometry to three equivalent Er and five equivalent B atoms. There are a spread of Rh–B bond distances ranging from 2.21–2.24 Å. B is bonded in a 6-coordinate geometry to three equivalent Er, five equivalent Rh, and one B atom. The B–B bond length is 1.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(BC)2 by Materials Project

ErB2C2 crystallizes in the tetragonal P4_2/mmc space group. The structure is three-dimensional. Er is bonded in a 8-coordinate geometry to eight equivalent B and eight equivalent C atoms. All Er–B bond lengths are 2.72 Å. All Er–C bond lengths are 2.69 Å. B is bonded in a 2-coordinate geometry to four equivalent Er and two equivalent C atoms. Both B–C bond lengths are 1.60 Å. C is bonded in a 2-coordinate geometry to four equivalent Er, two equivalent B, and one C atom. The C–C bond length is 1.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(PO3)3 by Materials Project

Er(PO3)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.22–2.28 Å. In the second Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.21–2.25 Å. In the third Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.24–2.26 Å. In the fourth Er3+ site, Er3+ is bonded to six O2- atoms to form ErO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.20–2.25 Å. There are nine inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–26°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–26°. There are a spread of P–O bond distances ranging from 1.49–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–45°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 27–34°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 29–30°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 26–36°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the seventh P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–26°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. In the eighth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 28–38°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the ninth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two ErO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–29°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. There are twenty-seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Er3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a linear geometry to one Er3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a linear geometry to one Er3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Er3+ and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom. In the twentieth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the twenty-first O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-sixth O2- site, O2- is bonded in a linear geometry to one Er3+ and one P5+ atom. In the twenty-seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Er3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(SiPt)2 by Materials Project

ErPt2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Er is bonded in a 8-coordinate geometry to eight equivalent Pt and eight equivalent Si atoms. All Er–Pt bond lengths are 3.25 Å. All Er–Si bond lengths are 3.28 Å. Pt is bonded in a 9-coordinate geometry to four equivalent Er and four equivalent Si atoms. All Pt–Si bond lengths are 2.41 Å. Si is bonded to four equivalent Er and four equivalent Pt atoms to form a mixture of distorted edge, face, and corner-sharing SiEr4Pt4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er by Materials Project

Er is Copper structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Er is bonded to twelve equivalent Er atoms to form a mixture of corner, edge, and face-sharing ErEr12 cuboctahedra. All Er–Er bond lengths are 3.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er by Materials Project

Er is Tungsten structured and crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Er is bonded in a distorted body-centered cubic geometry to eight equivalent Er atoms. All Er–Er bond lengths are 3.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er by Materials Project

Er is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Er is bonded to twelve equivalent Er atoms to form a mixture of face, edge, and corner-sharing ErEr12 cuboctahedra. There are six shorter (3.46 Å) and six longer (3.59 Å) Er–Er bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Optical and microstructural characterization of Er 3+ doped epitaxial cerium oxide on silicon

Rare-earth ion dopants in solid-state hosts are ideal candidates for quantum communication technologies, such as quantum memories, due to the intrinsic spin–photon interface of the rare-earth ion combined with the integration methods available in the solid state. Erbium-doped cerium oxide (Er:CeO 2 ) is a particularly promising host material platform for such a quantum memory, as it combines the telecom-wavelength (~ 1.5 μm) 4f–4f transition of erbium, a predicted long electron spin coherence time when embedded in CeO 2 , and a small lattice mismatch with silicon. In this work, we report on the epitaxial growth of Er:CeO 2 thin films on silicon using molecular beam epitaxy, with controlled erbium concentration between 2 and 130 parts per million (ppm). We carry out a detailed microstructural study to verify the CeO 2 host structure and characterize the spin and optical properties of the embedded Er 3+ ions as a function of doping density. In as-grown Er:CeO 2 in the 2–3 ppm regime, we identify an EPR linewidth of 245(1) MHz, an optical inhomogeneous linewidth of 9.5(2) GHz, an optical excited state lifetime of 3.5(1) ms, and a spectral diffusion-limited homogeneous linewidth as narrow as 4.8(3) MHz. We test the annealing of Er:CeO 2 films up to 900 °C, which yields narrowing of the inhomogeneous linewidth by 20% and extension of the excited state lifetime by 40%.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Lifetime measurements of 0 + states in Er 168 with the Doppler-shift attenuation method

Here, the lowest-lying shape oscillations of deformed nuclei have been described as quadrupole in nature (λ = 2), resulting in two types of vibrations or oscillations: β vibrations with oscillations along the symmetry axis (K π = 0 + ) and γ vibrations breaking axial symmetry with a projection of K π = 2 + on the symmetry axis. The γ vibration seems to be well characterized as the first K π = $2^+_1$ (or $2^+_γ$) band in deformed nuclei and exhibits a systematic behavior across the region. The nature of the K π = 0 + excitations, however, has remained poorly understood and has been open to debate for some decades. The goal of this work is to understand the nature of 0 + states observed in 168 Er through measurements of the lifetimes of these states and to determine if they are consistent with oscillations built on a deformed ground state, the minima of other coexisting shapes, single-particle states, or a mixture of effects. Lifetimes of excited states in the 168 Er nucleus were measured with the Doppler Shift Attenuation Method (DSAM) and the inelastic neutron scattering reaction, (n, n'γ), at the University of Kentucky Accelerator Laboratory. Numerous 0 + states had been observed by the (p, t) reaction. We confirm the 0 + states at 1217.2, 1421.5, 1833.6, 2364.9, 2392.1, and 2643.0 keV in 168 Er. We could not, however, support the previous assignments of 0 + levels at 2114.1, 2200.6, 2572.5, and 2617.4 keV. We report measured lifetimes for six confirmed 0 + excitations and additional members of 0 + bands. The results for 168 Er show that it is the third excited K π = 0 + ($0^+_4$) excitation that carries the collective strength and, therefore, the potential to be an oscillation on the ground state. This result is similar to the case in 166 Er, where it was also the $0^+_4$ state that exhibited greater collectivity than the first excited K π = 0 + band. The Delaroche et al. prediction for a collective K π = 0 + band is at E T =1.818 MeV which corresponds the third excited K π = 0 + band.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1988

Temperature and horizontal wind measurements on the ER-2 aircraft during the 1987 airborne Antarctic ozone experiment

The NASA ER-2 aircraft is equipped with special instrumentation to provide accurate in situ measurement of the atmospheric state variables during flight. The Meteorological Measurement System (MMS) on the ER-2 aircraft is described. Since the meteorological parameters (temperature, pressure, and wind vector) are extensively used by other ER-2 experimenters for data processing and interpretation, the accuracy and resolution of each of these parameters are assessed and discussed. During the 1987 Airborne Antarctic Ozone Experiment (AAOE) mission, the ER-2 aircraft was stationed at Punta Arenas, Chile (53 S, 72 W), and successfully flew over Antarctica on 12 occasions between August 17 and September 22, 1987. On each of the 12 flights, the ER-2 aircraft flight plan was to take off at approximately the same local time, fly southward at a near constant potential temperature surface, descend and ascend at the southernmost terminus at about 72 S over Antarctica and return northward at either the same or a different constant potential temperature surface. The measurements of the MMS experiment during the AAOE mission are presented. MMS data are organized to provide a composite view of the polar atmosphere, which is characterized by frigid temperatures and high zonal winds. Altitudinal variations of the temperature measurement (during takeoff/landing at Punta Arenas and during descent/ascent at the southern terminus) and latitudinal variations of the zonal wind (on near constant potential temperature surfaces) are emphasized and discussed.

Chan, K. Roland↗
NASA NTRS1992

Comparisons of the NASA ER-2 meteorological measurement system with radar tracking and radiosonde data

Measurements of aircraft longitude, latitude, and velocity, and measurements of atmospheric pressure, temperature, and horizontal wind from the meteorological measurement system (MMS) on board the NASA ER-2 aircraft were compared with independent measurements of these quantities from radiosondes and radar tracking of both the ER-2 and radiosonde balloons. In general, the comparisons were good and within the expected measurement accuracy and natural variability of the meteorological parameters. Radar tracking of the ER-2 resolved the velocity and position drift of the inertial navigation system (INS). The rms errors in the horizontal velocity components of the ER-2, due to INS errors, were found to be 0.5 m/s. The magnitude of the drift in longitude and latitude depends on the sign and magnitude of the corresponding component velocity drift and can be a few hundredths of a degree. The radar altitudes of the ER-2 and radiosondes were used as the basis for comparing measurements of atmospheric pressure, temperature, and horizontal wind from these two platforms. The uncertainty in the MMS horizontal wind measurement is estimated to be +/- 2.5 m/s. The accuracy of the MMS pressure and temperature measurements were inferred to be +/- 0.3 hPa and +/- 0.3 K.

Gaines, Steven E.↗
NASA NTRS1999

ER-2 Observations of Precipitation Systems During TRMM-LBA

The NASA ER-2 performed numerous flights over precipitation systems in Rondonia, Brazil. The ER-2 carried a payload including the ER-2 Doppler Radar (EDOP), the Advanced Microwave Precipitation Radiometer (AMPR), the Lightning Instrument Package, and other instruments. This presentation will overview the types of data sets collected during TRMM-LBA (Tropical Rainfall Measuring Mission Satellite-Large Scale Biosphere Atmosphere Experiment in Amazonia) with particular emphasis on EDOP measurements. Numerous cases of convection ranging from weak to very intense, were overflown by the ER-2. Two TRMM overpasses were coincident with ER-2 flights which allowed for intercomparisons between the Precipitation Radiometer (PR), EDOP, and the S-POL (S-band Polarimetric Radar) and TOGA (Tropical Oceans and Global Atmosphere) ground-based radars. Preliminary results from this comparison will be presented as well as initial selection of case studies and efforts involving vertical motions in convection.

Heymsfield, Gerald↗
NASA NTRS1999

ER-2 Observations of Precipitation Systems During TRMM-LBA

The NASA ER-2 performed numerous flights over precipitation systems in Rondonia, Brazil. The ER-2 carried a payload including the ER-2 Doppler Radar (EDOP), the Advanced Microwave Precipitation Radiometer (AMPR), the Lightning Instrument Package, and other instruments. This presentation will overview the types of data sets collected during TRMM-LBA with particular emphasis on EDOP measurements. Numerous cases of convection ranging from weak to very intense, were overflown by the ER-2. Two TRMM overpasses were coincident with ER-2 flights which allowed for intercomparisons between the Precipitation Radiometer (PR), EDOP, and the S-POL and TOGA ground-based radars. Preliminary results from this comparison will be presented as well as initial selection of case studies and efforts involving vertical motions in convection.

Heymsfield, Gerald↗
NASA NTRS2001

Comparison of ER-2 Aircraft and POAM-III, MLS, and SAGE-II Satellite Measurements During SOLVE Using Traditional Correlative Analysis and Trajectory Hunting Technique

We compared the version 5 Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS), version 3 Polar Ozone and Aerosol Measurement-III (POAM-111) aboard the French satellite SPOT-IV, version 6.0 Stratospheric Aerosol and Gas Experiment 11 (SAGE-II) aboard the Earth Radiation Budget Satellite, and NASA ER-2 aircraft measurements made in the northern hemisphere in January-February 2000 during the SAGE III Ozone Loss and Validation Experiment (SOLVE). This study addresses one of the key scientific objectives of the SOLVE campaign, namely, to validate multi-platform satellite measurements made in the polar stratosphere during winter. This intercomparison was performed using a traditional correlative analysis (TCA) and a trajectory hunting technique (THT). Launching backward and forward trajectories from the points of measurement, the THT identifies air parcels sampled at least twice within a prescribed match criterion during the course of 5 days. We found that the ozone measurements made by these four instruments agree most of the time within 110% in the stratosphere up to 1400 K (approximately 35 km). The water vapor measurements from POAM-III and the ER-2 Harvard Lyman-alpha hygrometer and JPL laser hygrometer agree to within 10.5 ppmv (or about +/-10%) in the lower stratosphere above 380 K. The MLS and ER-2 ClO measurements agree within their error bars for the TCA. The MLS and ER-2 nitric acid measurements near 17-20 km altitude agree within their uncertainties most of the time with a hint of a positive offset by MLS according to the TCA. We also applied the AER box model constrained by the ER-2 measurements for analysis of the ClO and HN03 measurements using the THT. We found that: (1) the model values of ClO are smaller by about 0.3-0.4 (0.2) ppbv below (above) 400 K than those by MLS and (2) the HN03 comparison shows a positive offset of MLS values by approximately 1 and 1-2 ppbv below 400 K and near 450 K, respectively. It is hard to quantify the HN03 offset in the 400-440 K range because of the high sensitivity of nitric acid to the PSC schemes. Our study shows that, with some limitations (like HN03 comparison under PSC conditions), the THT is a more powerful tool for validation studies than the TCA, making conclusions of the comparison statistically more robust.

Danilin, M. Y.↗
NASA NTRS1994

(abstract) Monitoring the Freeze/Thaw Transitions in Taiga Forests Using ERS-1 SAR

Automated recording stations have been installed at the Bonanza Creek Experimental Forest, a Long Term Ecological Research (LTER) site located near Fairbanks, Alaska, in a forest stand of the Tanana River floodplain underlain by discontinuous permafrost. These stations provide a continuous record of dielectric constant and temperature of tree trunks, and soil moisture and temperature profiles down to the root zone. Along with the weather stations deployed at the same location, these measurements provide a continuous record of the environmental and phenologic conditions of the forest during a complete seasonal cycle. At the same time, ERS-1 SAR imaged the study site repeatedly from space to provide radar backscatter measurements of the forest approximately three times a month. Here, we examine the temporal dynamic of ERS-1 SAR measurements in relation with the changing environmental and phenologic state of the forest canopy and of the forest ground layers during the winter/spring and fall/winter transitions of 1992 and 1993. During these transitions, we examine whether changes in radar backscatter observed by ERS-1 may be related to freezing or thawing of the soil and vegetation in order to determine the start and end of the growing season for the forest. The results of this analysis are used in turn to determine whether similar changes are observed over larger regions. Mosaics of SAR data generated along three different North-South Alaskan ERS-1 transects that intercept with our study site are used in combination with hourly air temperature and daily precipitation rates gathered at airport weather stations by the National Weather Service. Results obtained using ERS-1 data collected from January 1992 to mid-1993 will be discussed.

permafrost temporal dynamics Alaska ecology radar ↗